This invention relates to novel electronic timepieces with solid state illumination digital display means. As the conventional electroluminescent digital display means of low power consumption, liquid crystal displays have been representatively and perhaps most broadly used.
When taking, as a most commonly known representative of field effect liquid crystal display structure broadly used nowadays in the field of electronic digital display timepieces, it comprises a mass of liquid crystal material which is sealed-in between an upper and a lower glass plate member through spacer means defining the peripheral mergin of the liquid crystal mass. This liquid crystal display cell further comprises upper and lower polarizer plates attached to respective glass plate members carrying thereon a respective pattern of transparent electrodes arranged to generate the field effect for the digital displaying service. The lower glass plate member is attached at the lower polarizer side with a reflecting layer or plate through a spacer.
The cell is mounted on an IC-block-carrying base board in proper registration with an electrodes pattern formed on the board and electrically connected with the pattern and mechanically fixed to the board by means of connectors, preferably in the form of conductive rubber laminated strips, for illuminating visible display of electrical informations coming from the integrated circuit.
According to practical experience in the use of liquid crystal digital display cells, the following various drawbacks have been encountered.
The interelectrode gap in the cell which is fitted in the electronic watch or the like should be maintained at a very fine and small distance such as less than 20 microns or so on account of highly crowded spacial requirements of the watch and of such limitation imposed by the working voltage value. Much labor and cost must be consumed therefore for sealed charge of liquid crystal mass in position, thereby a mass production of these cells being substantially disturbed.
As a second drawback, although the charging quantity of the liquid crystal material is very small for each display cell, severe and precise caution must be paid for control of its aqueous and the like foreign matter content during preservation for the positive and advance prevention of otherwise invited later deterioration of the liquid crystal characteristics.
It has been further experienced during an elongated use of the liquid crystal cell that the electrolytic reaction is caused to take place within the liquid crystal material by application of voltage between the display electrodes which accelerates the deterioration of the material and substantially inhibits the rather preferable d.c. voltage application.
The aforementioned specific seal-in structure of the liquid crystal cell, the finished shape of the latter is substantially limited to square, rectangular or circular one.
A main object of the present invention is to provide an electronic digital display timepiece having improved digital display means more reliable in its operation for an extended time period and rather easy in assembly to the timepiece proper.
It is a further object of the invention to provide an electronic digital display timepiece having improved digital display means of a satisfactory illuminating performance with simpler structure.
It is a still further object of the invention to provide an electronic digital display timepiece having an irregular shaped display surface area.
A still another object of the invention is to provide an electronic timepiece of the above kind, having a number of display elements which can be driven with d.c. or a.c. low voltage signals.